Anti blow-off means for circuit breaker contacts

ABSTRACT

The movable contact structure of a very high current capacity molded case circuit breaker is provided with means to prevent blowoff forces from opening the arcing contact prior to opening movement of the contact carrier.

United States Patent Gryctko Feb. 12, 1974 [54] ANTI BLOW-OFF MEANS FORCIRCUIT 3,158,720 11/1964 Wiktor 200/!46 R BREAKER CONTACTS 3,513,2755/1970 Cellerini et a]. 200/146 R [75] Inventor: Carl E. Gryctko, HaddonHeights,

NJ. Primary ExaminerRobert S. Macon Assign: Imperial CorporationAttorney, Agent, or firm-Ostrolenk, Faber, Gerb &

Philadelphia, Pa. Soffen [22] Filed: July 27, 1972 [21] Appl. No.:275,522

[ ABSTRACT 52 US. Cl 200/146 R The movable Contact Structure f a veryhigh current [51] Int. Cl. H0lh 33/12 capacity molded case circuitbreaker is provided with [58] F'eld of Search 200/146 144 147 R means toprevent blowoff forces from opening the arcing contact prior to openingmovement of the contact [56] References Cited carrier UNITED STATESPATENTS 3,076,882 2/l963 Judd et al. 200/146 R 7 Claims, 7 DrawingFigures l I M Z SPZ/AfPO/dffiffl Z I t auae Cf/ZZ} 1 1 70 15-)" Z/ /d\0/ r/wma/z 1 N W6 ll 3 J 47 l I I II o I 4' I O i I/ t 9 I 2g 27 2 29 MZ5 25 "All ANTI BLOW-OF F MEANS FOR CIRCUIT BREAKER CONTACTS Thisinvention relates to high current molded case circuit breakersin generaland more particularly relates to an anti-blowoff adjustment for themovable contacts thereof.

Molded case circuit breakers of very high current rating are providedwith one or more movable main contacts for carrying current on acontinuous basis and a movable arcing contact for current interruption.Typically, the arcing and main contacts are mounted to the same carrierin a manner to produce a contact operation sequence in which the arcingcontacts close before the main contacts when the circuit breaker isbeing closed and the main contacts separate before the arcing contactswhen the circuit breaker is being opened. However, when extremely highcurrents are being interrupted, very high blowoff forces are present,with the result that intended contact opening and closing sequences maybe upset. That is, severe blowoff forces may cause separation of thearcing contacts prior to separation of the main contacts, in which eventcircuit interruption may be initiated at the main contacts, therebycausing excessive pitting thereof. This out-ofnormal sequence contactseparation is most likely to happen when the contact carrier is inclosed circuit position and with the toggle of the contact operatingmechanism just passing over center in the opening direction, at whichtime contact pressure forces usually supplied by the'mechanism operatingsprings are relaxed so that the contact carrier is effectively floating.

In accordance with the instant invention, an adjustable stop mounted tothe contact carrier is adjusted, after closing of the contacts, to aposition which limits movement of the arcing contact toward the contactcarrier to the relative positions occupied by these elements when thecontacts are closed. Thus, the arcing contacts may not open until thecontact carrier begins to move toward open circuit position.

In another embodiment of this invention, additional stops are providedto prevent open circuit movement of both the arcing and main contactsprior to movement of the contact carrier toward-open circuit position.In still another embodiment of this invention all of the main contactsare connected to the arcing contact by levers so constructed thatmovement of a main contact toward open circuit position relative to thecontact carrier exerts a force tending to close the arcing contact.

Accordingly, a primary object of the instant invention is to providenovel means for protecting circuit breaker contacts against pitting.

Another object is to provide a contact carrier bridge with adjustablestop means settable to engage the movable arcing contacts and limitmovement thereof toward the contact bridge.

Still another object is to provide a plurality of adjustable stops onthe contact carrier, engageable with the main arcing contacts to limitmovement of these contacts towards the contact bridge to the relativepositions occupied thereby with the circuit breaker closed.

These objects as well as other objects of this invention will becomereadily apparent after reading the following description of theaccompanying drawings in which:

FIG. 1 is a longitudinal section, taken through line 1-l of FIG. 2,showing a circuit breaker contact mechanism, including anti-blowoffadjusting means constructed in accordance with the instant invention.

FIG. 2 is a plan view of the contact bridge, looking in the direction ofarrows 2-2 of FIG. 1.

FIG. 3 is a view similar to FIG. 1 showing a fragmentary portion of acontact mechanism provided with another embodiment of a stop meansconstructed in accordance with the instant invention.

FIG. 4 is an end view, looking in the direction of arrows 44 of FIG. 3,showing the contacts and antiblowoff lever mechanism.

FIG. 5 is a view similar to FIG. 1, showing still another embodiment ofthe instant invention.

FIG. 6 is an end view looking in the direction of arrows 66 of FIG. 5,showing the contacts and antiblowoff means.

FIG. 7 is a plan view, looking in the direction of arrows 77 of FIG. 5,showing the contact carrier bridge and the anti-blowoff elements mountedthereto.

Now referring more particularly to FIGS. 1 and 2. Contact carrier bridge10 is generally of inverted U- shape and is provided with rearwardlyextending arms 11 pivotally connected at bushing 12 to the frame (notshown) of spring powered overcenter toggle-type operating mechanism 14.Mechanism 14 is connected to shaft 15 whose ends are supported bycarrier arms 11. Shaft 15 provides the pivot for arcing contact arm 21and a plurality of arms 22 for front main contacts 25. Another shaft 16,whose ends are supported by carrier arms 11, provides a pivot for theplurality of arms 23 for rear main contacts 26.

In the closed position of contact carrier 10, illustrated in FIG. 1,coiled compression springs 31 extending through the open bottom oftubular housing 32 on carrier 10 biases movable arcing contact 24 intoengagement with stationary arcing contact 27. Individual coiledcompression springs 34 extending through the bottoms of individualtubular members 35 mounted to carrier 10 bias each of the front movablemain contacts 25 into engagement with stationary main contacts 28. Twoinverted U-shaped auxiliary contact carriers 36 are disposed with theirarms extending downward through apertures 41, 42, 43 of contact carrier10 to support a pair of contact arms 23 on an individual stub shaft 44for each pair of contact arms 23. Individual coiled compression springs45 bias each of the auxiliary carriers 36 downward with respect tocontact carrier 10.

A pair of anti-blowoff adjusting screws 47 are threadably mounted tosupport strip 48, with the lower ends of stop screws 47 engaging theupper edge of arcing contact arm 21 when contact carrier 10 is in theclosed circuit position shown in FIG. 1. The body portions of screws 47extend through contact carrier aperture 42, with support strip 48bridging aperture 42 and the heads of screws 47 being accessible fromabove contact carrier 10. The presence of stop screws 47,adjusted asshown in FIG. 1, prevents blowoff forces from separating arcing contacts24, 27 unless contact carrier 10 is also moving toward its open circuitposition.

For the emodiment of FIGS. 3 and 4, the drawings do not show the springsprovided for biasing arcing contact arms 51 and main contact arms 52, 53downward with respect to contact carrier 54. Carrier 54 is provided withdownwardly extending centrally located ear 56 supporting stub shaft 55which pivotally mounts four levers 61, 63, 62. 64, at pointsintermediate the ends thereof. The end of the longer arms of each of thelevers 61-64 engagesthe upper end of an individual main contact arm 52,and the end of the shorter arm of each of the levers 61-64 engages theupper edge of arcing contact arm 51. Thus, any tendency of main contactarms 52 to move upward relative to carrier 54 is transmitted throughlevers 61-64 to urge arcing contact 51 downward, and the reaction forceto this downward force acting on arcing contact 51 exerts an upwardforce on contact carrier 54.

In the embodiment of FIGS. -7, adjustable stop 71 threadably mounted tocontact carrier 70, engages the upper edge of arcing contact arm 72 toserve the same function as stop screws 47 of FIGS. 1 and 2. Contactcarrier 70 also threadably mounts inverted stop screws 74a, 74b. Thehead of stop screw 74a is seated against the upper edges of main contactarms 73a, 73b, and in a similar manner the head of stop screw 74b isseated against the upper edges of main contact arm 73c and 73d. Thus,blowoff forces acting to separate arcing contacts 76, 77 and/or any ofthe pairs of main contacts 78, 79 exert forces that are transmitteddirectly to contact carrier 70 and urge upward movement thereof to acircuit open position.

For those features of construction in circuit breaker that have not beendescribed in detail herein, reference is made to one or more of thecopending applications Ser. Nos. 275,568, 275,577, 275,446, 275,578,275,454, 275,508, 275,621, 275,623, 275,569, 275,569, 275,521, 275,523,and 275,622, all filed on even date herewith and all assigned to theassignee of the instant invention.

Although there have been described preferred embodiments of this novelinvention, many variations and modifications will now become apparent tothose skilled in the art. Therefore, this invention is to be limited notby the specific disclosure herein but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows.

1. Circuit breaker contact means including a stationary portion and amovable portion operable into and out of engagement with said stationaryportion; said movable portion including arcing contact means and maincontact means; carrier means to which said arcing and main contact meansare mounted for independent relative movement with respect thereto andbodily movement therewith; biasing means urging said arcing and maincontact means away from said carrier means and toward said stationaryportion; means to limit relative movement of said arcing and maincontact means from the stationary portion; stop means to preventmovement of said arcing contact means away from said stationary portionbefore movement of said carrier means from said closed circuit positiontoward said open circuit position.

2. Circuit breaker means as set forth in claim 1 in which there is anadjustable stop means to limit movement of said main contact meanstoward said carrier means to the relative positions of said main contactmeans and said carrier means at a time when the latter is in said closedcircuit position and the main contact means is engaged with thestationary portion.

3. A circuit breaker as set forth in claim 1 in which the arcing andmain contact means are pivotally mounted on the contact carrier, withsaid arcing contact means being interposed between portions of said maincontact means.

4. A circuit breaker as set forth in claim 1 in which the stop means'isadjustable and is set to limit movement of said arcing contact meanstoward said carrier means to the relative positions of said arcingcontact means and said carrier means at a time when the latter is insaid closed circuit position and the arcing contact means is engagedwith the stationary portion.

5. Circuit breaker means as set forth in claim 4 in which there is anadjustable stop means to limit movement of said main contact meanstoward said carrier means to the relative positions of said main contactmeans and said carrier means at a time when the latter is in said closedcircuit position and the main contact means is engaged with thestationary portion.

6. A circuit breaker as set forth in claim 1 in which the stop meansincludes levers connected between said arcing contact means and saidmain contact means;

forces to said arcing contact means than are applied to 7 said movablecontact means.

1. Circuit breaker contact means including a stationary portion and amovable portion operable into and out of engagement with said stationaryportion; said movable portion including arcing contact means and maincontact means; carrier means to which said arcing and main contact meansare mounted for independent relative movement with respect thereto andbodily movement therewith; biasing means urging said arcing and maincontact means away from said carrier means and toward said stationaryportion; means to limit relative movement of said arcing and maincontact means toward said stationary portion when said carrier means isin an open circuit position; said contact means being mounted to saidcarrier means in a manner such that under normal operating conditions,as saId carrier means moves toward said stationary portion to a closedcircuit position, said arcing contact means will engage said stationaryportion prior to engagement of the latter by said main contact means,and as said carrier means moves from closed to open circuit positionsaid main contact means will separate from said stationary portion priorto separation of the arcing contact means from the stationary portion;stop means to prevent movement of said arcing contact means away fromsaid stationary portion before movement of said carrier means from saidclosed circuit position toward said open circuit position.
 2. Circuitbreaker means as set forth in claim 1 in which there is an adjustablestop means to limit movement of said main contact means toward saidcarrier means to the relative positions of said main contact means andsaid carrier means at a time when the latter is in said closed circuitposition and the main contact means is engaged with the stationaryportion.
 3. A circuit breaker as set forth in claim 1 in which thearcing and main contact means are pivotally mounted on the contactcarrier, with said arcing contact means being interposed betweenportions of said main contact means.
 4. A circuit breaker as set forthin claim 1 in which the stop means is adjustable and is set to limitmovement of said arcing contact means toward said carrier means to therelative positions of said arcing contact means and said carrier meansat a time when the latter is in said closed circuit position and thearcing contact means is engaged with the stationary portion.
 5. Circuitbreaker means as set forth in claim 4 in which there is an adjustablestop Means to limit movement of said main contact means toward saidcarrier means to the relative positions of said main contact means andsaid carrier means at a time when the latter is in said closed circuitposition and the main contact means is engaged with the stationaryportion.
 6. A circuit breaker as set forth in claim 1 in which the stopmeans includes levers connected between said arcing contact means andsaid main contact means; said levers being mounted so that forces movingsaid main contact means toward said carrier means exert forces on saidarcing contact means urging the latter away from said carrier means. 7.A circuit breaker as set forth in claim 6 in which the levers aremounted and positioned to apply greater forces to said arcing contactmeans than are applied to said movable contact means.